Multi-gas centrally cooled showerhead design

ABSTRACT

A method and apparatus for chemical vapor deposition and/or hydride vapor phase epitaxial deposition are provided. The apparatus generally include a lower bottom plate and an upper bottom plate defining a first plenum. The upper bottom plate and a mid-plate positioned above the upper bottom plate define a heat exchanging channel. The mid-plate and a top plate positioned above the mid-plate define a second plenum. A plurality of gas conduits extend from the second plenum through the heat exchanging channel and the first plenum. The method generally includes flowing a first gas through a first plenum into a processing region, and flowing a second gas through a second plenum into a processing region. A heat exchanging fluid is introduced to a heat exchanging channel disposed between the first plenum and the second plenum. The first gas and the second gas are then reacted to form a film on a substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to methods andapparatus for chemical vapor deposition (CVD) on a substrate, and, inparticular, to a showerhead design for use in metal organic chemicalvapor deposition and/or hydride vapor phase epitaxy (HVPE).

2. Description of the Related Art

Group III-V films are finding greater importance in the development andfabrication of a variety of semiconductor devices, such as shortwavelength light emitting diodes (LEDs), laser diodes (LDs), andelectronic devices including high power, high frequency, hightemperature transistors and integrated circuits. For example, shortwavelength (e.g., blue/green to ultraviolet) LEDs are fabricated usingthe Group III-nitride semiconducting material gallium nitride. It hasbeen observed that short wavelength LEDs fabricated using galliumnitride can provide significantly greater efficiencies and longeroperating lifetimes than short wavelength LEDs fabricated usingnon-nitride semiconducting materials, such as Group II-VI materials.

One method that has been used for depositing Group III-nitrides, such asgallium nitride, is metal organic chemical vapor deposition (MOCVD).This chemical vapor deposition method is generally performed in areactor having a temperature controlled environment to assure thestability of a first process gas which contains at least one elementfrom Group III, such as gallium. A second process gas, such as ammonia,provides the nitrogen needed to form a Group III-nitride. The twoprocess gases are injected into a processing zone within the reactorwhere they mix and move towards a heated substrate in the processingzone. A carrier gas may be used to assist in the transport of theprocess gases towards the substrate. The precursors react at the surfaceof the heated substrate to form a Group III-nitride layer on thesubstrate surface. The quality of the film depends in part upondeposition uniformity which, in turn, depends upon uniform mixing of theprecursors across the substrate.

Multiple substrates may be arranged on a substrate carrier and eachsubstrate may have a diameter ranging from 50 mm to 100 mm or larger.The uniform mixing of precursors over larger substrates and/or moresubstrates and larger deposition areas is desirable in order to increaseyield and throughput. These factors are important since they directlyaffect the cost to produce an electronic device and, thus, a devicemanufacturer's competitiveness in the market place.

Interaction of the process gases with the hot hardware components, whichare often found in the processing zone of an LED or LD forming reactor,will generally cause the precursor to break-down and deposit on thesehot surfaces. Typically, the hot reactor surfaces are formed byradiation from the heat sources used to heat the substrates. Thedeposition of the precursor materials on the hot surfaces can beespecially problematic when it occurs in or on the precursordistribution components, such as the showerhead. Deposition on theprecursor distribution components will affect the flow distributionuniformity over time. Therefore, there is a need for a gas distributionapparatus that prevents or reduces the likelihood that the MOCVD or HVPEprecursors will be heated to a temperature that will cause them to breakdown and affect the performance of the gas distribution device.

Also, as the demand for LEDs, LDs, transistors, and integrated circuitsincreases, the efficiency of depositing high quality Group-III nitridefilms takes on greater importance. Therefore, there is a need for animproved deposition apparatus and process that can provide consistentfilm quality over larger substrates and larger deposition areas.

SUMMARY OF THE INVENTION

A method and apparatus that may be utilized for chemical vapordeposition and/or hydride vapor phase epitaxial deposition are provided.The apparatus generally include a lower bottom plate and an upper bottomplate defining a first plenum. The upper bottom plate and a mid-platepositioned above the upper bottom plate define a heat exchangingchannel. The mid-plate and a top plate positioned above the mid-platedefine a second plenum. A plurality of gas conduits extend from thesecond plenum through the heat exchanging channel and the first plenum.The method generally includes flowing a first gas through a first plenuminto a processing region, and flowing a second gas through a secondplenum into a processing region. A heat exchanging fluid is introducedto a heat exchanging channel disposed between the first plenum and thesecond plenum. The temperature of the first gas is greater than thetemperature of the second gas when the first gas and the second gasenter the processing region. The first gas and the second gas are thenreacted to form a film on a substrate.

One embodiment provides an apparatus comprising a lower bottom plate andan upper bottom plate positioned above the lower bottom plate. The upperbottom plate and the lower bottom plate define a first plenum. Amid-plate is positioned above the upper bottom plate. The mid-plate andthe upper bottom plate define a heat exchanging channel for containing aheat exchanging fluid. A top plate is positioned above the mid-plate.The top plate and the mid-plate define a second plenum. A plurality offirst gas conduits extend from the second plenum through the heatexchanging channel and the first plenum. Each of the plurality of firstgas conduits are in fluid communication with the second plenum and aprocessing region of a processing chamber.

In another embodiment, an apparatus comprises a lower bottom plate andan upper bottom plate positioned above the lower bottom plate. The upperbottom plate and the lower bottom plate define a first plenum. Aplurality of first gas conduits are in fluid communication with thefirst plenum and a processing region of a process chamber. A mid-plateis positioned above the upper bottom plate. The mid-plate and the upperbottom plate define a heat exchanging channel for containing a heatexchanging fluid. A top plate is positioned above the mid-plate. The topplate and the mid-plate define a second plenum. The showerhead apparatusalso comprises a plurality of second gas conduits in fluid communicationwith the second plenum and the processing region. The plurality ofsecond gas conduits extend through the first plenum and the heatexchanging channel. Each of the first gas conduits has a second gasconduit that is disposed within the boundary of the first gas conduit.

In another embodiment, a method comprises flowing a first gas through afirst plenum of a showerhead apparatus and into a processing region of achamber. A second gas is flown through a second plenum of the showerheadapparatus and into the processing region of the chamber. The secondplenum is fluidly coupled to the processing region through a pluralityof gas conduits. A heat exchanging fluid is introduced to a heatexchanging channel disposed between the first plenum and the secondplenum. The plurality of gas conduits extend through the heat exchangingchannel. The first gas and the second gas are reacted in the processingregion to form a film on the substrate, and the temperature of the firstgas is greater than the temperature of the second gas when the first gasand the second gas enter the processing region.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic view of a deposition apparatus according to oneembodiment of the invention.

FIG. 2 is a cross sectional view of an embodiment of a showerheadassembly.

FIG. 3 is a partial cross sectional view of another embodiment of ashowerhead assembly.

FIG. 4A is a partial schematic bottom view of the showerhead assemblyshown in FIG. 3 according to an embodiment of the invention.

FIG. 4B is a partial schematic bottom view of the showerhead assemblyshown in FIG. 2 according to an embodiment of the invention.

FIG. 4C is a partial schematic bottom view of the showerhead assemblyshown in FIG. 2 according to an embodiment of the invention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

A method and apparatus that may be utilized for chemical vapordeposition and/or hydride vapor phase epitaxial deposition are provided.The apparatus generally include a lower bottom plate and an upper bottomplate defining a first plenum. The upper bottom plate and a mid-platepositioned above the upper bottom plate define a heat exchangingchannel. The mid-plate and a top plate positioned above the mid-platedefine a second plenum. A plurality of gas conduits extend from thesecond plenum through the heat exchanging channel and the first plenum.The method generally includes flowing a first gas through the firstplenum into a processing region and flowing a second gas through thesecond plenum into a processing region. A heat exchanging fluid isintroduced to a heat exchanging channel disposed between the firstplenum and the second plenum. The temperature of the first gas isgreater than the temperature of the second gas when the first gas andthe second gas enter the processing region. The first gas and the secondgas are then reacted to form a film on a substrate.

Systems and chambers that may be adapted to practice the presentinvention are described in U.S. patent application Ser. No. 11/404,516,filed on Apr. 14, 2006, and Ser. No. 11/429,022, filed May 5, 2005, bothof which are incorporated by reference in their entireties. It iscontemplated that other systems and chambers may also benefit fromembodiments described herein.

FIG. 1 is a schematic view of a deposition apparatus according to oneembodiment of the invention. The apparatus 100 includes a chamber 102, agas delivery system 125, a remote plasma source 126, and a vacuum system112. The chamber 102 includes a chamber body 103 that encloses aprocessing region 108 and a lower volume 110. A showerhead assembly 104is disposed at one end of the chamber body 103, while a lower dome 119is disposed at another end of the chamber body 103. A processing region108 and a lower volume 110 are located between the showerhead assembly104 and a lower dome 119 within the chamber body 103. A substratecarrier 114 is disposed between the processing region 108 and the lowervolume 119. Thus, the lower volume 110 is defined by the lower dome 119and the substrate carrier 114, while the processing region 108 isdefined by the showerhead assembly 104 and the substrate carrier 114.The substrate carrier 114 is shown in the process position, but may bemoved to a lower position where the substrates 140 may be loaded orunloaded. An exhaust ring 120 is disposed around the periphery of thesubstrate carrier 114 to help prevent deposition from occurring in thelower volume 110 and to also help direct exhaust gases from the chamber102 to exhaust ports 109.

Radiant heating may be provided by a plurality of inner lamps 121A andouter lamps 121B disposed below the lower dome 119 to effect heating ofsubstrates 140, substrate carrier 114, or process gases located withinprocessing region 108. The lower dome 119 is made of transparentmaterial, such as high-purity quartz, to allow light to passtherethrough from the plurality of inner lamps 121A and outer lamps121B. Reflectors 166 may be used to direct the radiant energy providedby inner and outer lamps 121A, 121B to the interior volume of chamber102. Additional rings of lamps may also be used for finer temperaturecontrol of the substrates 140.

The plurality of inner and outer lamps 121A, 121B may be arranged inconcentric circles or zones (not shown), and each lamp zone may beseparately powered. One or more temperature sensors, such as pyrometers(not shown), may be disposed within the showerhead assembly 104 tomeasure substrate 140 and substrate carrier 114 temperatures. Thetemperature data may be sent to a controller 199 which can adjust powerto separate lamp zones to maintain a predetermined temperature profileacross the substrate carrier 114. Additionally, the power to separatelamp zones can be adjusted to compensate for precursor flow or precursorconcentration non-uniformity. For example, if the precursorconcentration is lower in a substrate carrier 114 region near an outerlamp zone, the power to the outer lamp zone may be adjusted to helpcompensate for the precursor depletion in this region.

The inner and outer lamps 121A, 121B may heat the substrates 140 to atemperature of about 400 degrees Celsius to about 1200 degrees Celsiusduring processing. It is to be understood that the heating source is notrestricted to the use of arrays of inner and outer lamps 121A, 121B. Anysuitable heating source may be utilized to ensure that the propertemperature is adequately applied to the chamber 102 and substrates 140therein. For example, the heating source may comprise resistive heatingelements which are in thermal contact with the substrate carrier 114.

The substrate carrier 114 includes one or more recesses 116 within whichone or more substrates 140 are disposed during processing. The substratecarrier 114 is formed from silicon carbide (SiC) and generally ranges insize from about 200 millimeters to about 750 millimeters. Alternatively,the substrate carrier 114 may be formed from SiC-coated graphite. Thesubstrate carrier 114 can rotate about an axis during processing. Forexample, the substrate carrier 114 may be rotated at about 2 RPM toabout 100 RPM, such as at about 30 RPM. Rotating the substrate carrier114 aids in providing uniform heating of the substrates 140 and uniformexposure of the processing gases to each substrate 140. Duringprocessing, the distance between the lower surface of showerheadassembly 104 and the substrate carrier 114 ranges from about 4 mm toabout 41 mm. The lower surface of showerhead assembly 104 is coplanarand faces the substrates 140 during processing.

The substrate carrier 114 is shown having two substrates 140 positionedwithin recesses 116. However, substrate carrier 114 may support six,eight, or more substrates during processing depending on the desiredthroughput. Typical substrates 140 may include sapphire, siliconcarbide, or silicon. It is contemplated that other types of substrates140, such as glass substrates 140, may also be processed. Substrate 140size may range from 50 mm-150 mm in diameter or larger. It is to beunderstood that substrates 140 of other sizes may be processed withinthe chamber 102 and according to the processes described herein.

A gas delivery system 125 is coupled to the showerhead apparatus 104 toprovide one or more gases to the processing region 108 duringprocessing. The gas delivery system 125 includes multiple gas sources131A and 132A coupled to supply lines 131 and 132, respectively, as wellas supply line 133. It is to be understood that the gas delivery system125 is not limited to two gas sources. Each supply line 131, 132 maycomprise a plurality of lines which are coupled to and in fluidcommunication with the showerhead assembly 104. Depending on the processbeing run, some of the sources may be liquid sources rather than gases,in which case the gas delivery system may include a liquid injectionsystem or other means (e.g., a bubbler) to vaporize the liquid. Thevapor may then be mixed with a carrier gas such as hydrogen (H₂),nitrogen (N₂), helium (He) or argon (Ar) prior to delivery to thechamber 102. Different gases, such as precursor gases, carrier gases,purge gases, cleaning/etching gases or others may be supplied from thegas delivery system 125 to separate supply lines 131, 132, and 133 tothe showerhead assembly 104. Furthermore, the supply lines 131, 132, and133 may include shut-off valves and mass flow controllers or other typesof controllers to monitor and regulate or shut off the flow of gas ineach line.

A conduit 129 receives cleaning and/or etching gases from a remoteplasma source 126. The remote plasma source 126 receives gases from thegas delivery system 125 via supply line 124. A valve 130 is disposedbetween the showerhead assembly 104 and remote plasma source 126 tocontrol the flow of gas between the remote plasma source 126 and theshowerhead assembly 104. The valve 130 may be opened to allow a cleaningand/or etching gas, including ionized gases, to flow into the showerheadassembly 104 via supply line 133. Additionally, the gas delivery system125 and remote plasma source 126 may be suitably adapted so that processgases from sources 131A and 132A may be supplied to the remote plasmasource 126 to produce plasma species which may be sent throughshowerhead assembly 104 to deposit CVD layers, such as III-V films, onsubstrates 140.

The remote plasma source 126 is a radio frequency plasma source adaptedfor chamber cleaning and/or substrate etching. Cleaning and/or etchinggas may be supplied to the remote plasma source 126 via supply line 124to produce plasma species which may be sent via conduit 129 and supplyline 133 for dispersion through showerhead assembly 104 into chamber102. Alternatively, cleaning/etching gases may be delivered from gasdelivery system 125 for non-plasma cleaning and/or etching usingalternate supply line configurations to showerhead assembly 104. Gasesfor a cleaning application may comprise a halogen containing gas, suchas fluorine or chlorine, or vapor comprising hydrochloric acid (HCl). Itis contemplated that plasma sources other than radio frequency plasmasources, for example microwave plasma sources, may also be used.

A purge gas (e.g., nitrogen) may be delivered into the chamber 102 fromthe showerhead assembly 104 and/or from inlet ports (not shown) disposedbelow the substrate carrier 114 near the bottom of the chamber body 103.The purge gas may be used to remove gases from the processing region 108after processing. In additional to purging the chamber 102, gas providedfrom inlet ports disposed below the substrate carrier 114 may alsoincrease the pressure within the lower volume 110 to contain processgases in the processing region 108, thereby reducing the deposition ofmaterial in undesired locations. The purge gas enters the lower volume110 of the chamber 102 and flows upwards past the substrate carrier 114and exhaust ring 120 and into multiple exhaust ports 109 which aredisposed around an annular exhaust channel 105. An exhaust conduit 106connects the annular exhaust channel 105 to a vacuum system 112 whichincludes a vacuum pump (not shown). The chamber pressure may becontrolled using a valve system 107 which controls the rate at which theexhaust gases are drawn from the annular exhaust channel 105. Duringprocessing, the draw of the annular exhaust channel 105 may affect gasflow so that the process gas introduced to the processing region 108flows substantially tangential to the substrates 140 and may beuniformly distributed radially across the substrate 140 depositionsurfaces in a laminar flow. The processing region 108 may be maintainedat a pressure of about 760 Torr down to about 80 Torr during processing.

The showerhead assembly 104 has a heat exchanging system 170 coupledthereto to assist in controlling the temperature of various componentsof the showerhead assembly 170. The heat exchanging system 170 comprisesa heat exchanger 170A that is coupled to the showerhead assembly 104 viaan inlet conduit 171 and an outlet conduit 172. A controller 199 iscoupled to the heat exchanger 170A to control the temperature of theshowerhead assembly 104.

FIG. 2 is a cross sectional view of an embodiment of a showerheadassembly. The showerhead assembly 104 comprises a top plate 230,mid-plate 210, an upper bottom plate 233A and a lower bottom plate 233B.The upper bottom plate 233A and the lower bottom plate 233B define thefirst plenum 244. The mid-plate 210 and upper bottom plate 233A definethe heat exchanging channel 275. The top plate 230 and the mid-plate 210define the second plenum 245.

The heat exchanging channel 275 is coupled to a heat exchanging system170 to control the temperature of the various surfaces of the showerheadassembly 104. The heat exchanging system 170 comprises a heat exchanger170A that is coupled to the one or more heat exchanging channels 275formed in the showerhead assembly 104 via an inlet conduit 171 and anoutlet conduit 172. The heat exchanging channel 275 through which a heatexchanging fluid flows is used to help regulate the temperature of theshowerhead assembly 104.

The heat exchanging channel 275 is disposed between the first plenum 244and the second plenum 245. The heat exchanging channel 275 encircles thegas conduits 247, which are disposed through mid-plate holes 240, bottomplate holes 250 and holes 251 in wall 285. Thus, the heat exchangingfluid can flow around and cool the gas or vapor flowing through acentral region 247A of the gas conduits 247 while the vapor flows intoprocessing region 108. The central region 247A of the gas conduits 247are in fluid communication with the second plenum 245 and the processingregion 108, thus permitting process gases to travel from the secondplenum 245 to the processing region 108. In this configuration, the heatexchanging channel 275 is disposed between the first plenum 244 andsecond plenum 245 to control the temperature of the gases or vapordelivered therethrough.

A central conduit 248 is disposed through the showerhead assembly 104 toprovide a cleaning and/or etching gas or plasma into the chamber body103. The central conduit 248 may receive cleaning and/or etching gas orplasma from supply line 133 and disperse the cleaning and/or etching gasinside chamber body 103 to provide more effective cleaning.Alternatively, cleaning and/or etching gas or plasma may be deliveredinto chamber body 103 through other routes, such as through the gasconduits 247 and/or conduits 281 in the showerhead assembly 104. Forplasma based etching or cleaning, fluorine or chlorine may be used Fornon-plasma based etching, halogen gases, such as Cl₂, Br, and I₂, orhalides, such as HCl, HBr, and HI may be used. The cleaning and/oretching gas is removed from the processing region 108 through theexhaust port 109, the exhaust channel 105, and the exhaust conduit 106.

The process gas 255 flows from the gas supply 132A through supply line132 into the second plenum 245 and into gas conduits 247, which are influid communication with the processing region 108. The process gas 254flows from gas supply 131A through the supply line 131 into the gasconduits 281 towards the processing region 108. The first plenum 244 isnot in fluid communication with the second plenum 245 so that the firstprocess gas 254 and the second process gas 255 remain isolated untilinjected into the processing region 108 located within the chamber body103. The process gas 254 and/or process gas 255 may comprise one or moreprecursor gases or other process gases, including carrier gases anddopant gases, to carry out desired processes within the processingregion 108. For example, process gas 254 and process gas 255 may containone or more precursors for deposition of a material on substrates 140positioned on substrate carrier 114.

The positioning of a heat exchanging channel 275 provides control of thetemperature of various showerhead assembly features, such as the gasconduits 247, the wall 280, and the showerhead face 283. Control of thetemperature of the showerhead assembly features is desirable to reduceor eliminate the formation of condensates on the showerhead assembly104. Control of the temperature of the various showerhead assemblyfeatures is also desirable to reduce gas phase particle formation and toprevent the production of undesirable precursor reactant products whichmay adversely affect the composition of the film deposited on thesubstrates 140. The showerhead temperature may be measured by one ormore thermocouples or other temperature sensors disposed in proximity toshowerhead face 283, heat exchanging channel 275, and/or wall 280.Additionally or alternatively, one or more thermocouples or othertemperature sensors may be disposed in proximity to the inlet conduit171 and/or the outlet conduit 172. The temperature data measured by theone or more thermocouples or other temperature sensors is sent to acontroller which may adjust the heat exchanging fluid temperature andflow rate to maintain the showerhead temperature within a predeterminedrange. The showerhead temperature is generally maintained at about 50degrees Celsius to about 350 degrees Celsius, but may also be maintainedat a temperature of greater than 350 degrees Celsius, if desired.

It is believed that a gas conduit and heat exchanging channelconfiguration that only requires half of the gas conduits (e.g., gasconduits 247) to extend through the heat exchanging channel 275 willgreatly reduce the chances of the heat exchanging fluid leaking into thefirst plenum 244 or second plenum 245 at the junctions formed betweenthe gas conduits (e.g., gas conduits 247) and the walls (e.g., walls 279and 280). Only half of the gas conduits are required to extend throughthe heat exchanging channel 275, since only one gas plenum (e.g., secondplenum 245) is disposed on one side of the heat exchanging channel 275opposite the processing region 108, while the gas exiting the firstplenum 244 enters directly into the processing region 108. Also, bypositioning the heat exchanging channel 275 so that it is not directlyadjacent to the processing region 108, the chances that a heatexchanging fluid leak will reach the processing region 108 is greatlyreduced. Thus, the chance of damage occurring to the chamber andsubstrates 140 is also reduced. It is also believed that the leakage ofthe heat exchanging fluid into the processing region 108 can bedangerous at the typical processing temperature used to form LED and LDproducts, such as greater than 750 degrees Celsius, due to the phasechange created as the liquid heat exchanging fluid turns into a gas.

The flow rate of the heat exchanging fluid may be adjusted to helpcontrol the temperature of the showerhead assembly 104. Additionally,the thickness of the walls 279 and 280 surrounding the heat exchangingchannel 275 may be designed to facilitate temperature regulation ofvarious showerhead surfaces. Suitable heat exchanging fluids includewater, water-based ethylene glycol mixtures, a perfluoropolyether (e.g.,GALDEN® fluid), oil-based thermal transfer fluids, or liquid metals suchas gallium or gallium alloy. The heat exchanging fluid is circulatedthrough a heat exchanger 170A to raise or lower the temperature of theheat exchanging fluid as required to maintain the temperature of theshowerhead assembly 104 within a desired temperature range. The heatexchanging fluid can be maintained at a temperature of 20 degreesCelsius or greater, depending on process requirements. For example, theheat exchanging fluid can be maintained at a temperature within a rangefrom about 20 degrees Celsius to about 120 degrees, or within a range ofabout 100 degrees Celsius to about 350 degrees Celsius. The heatexchanging fluid may also be heated above its boiling point so that theshowerhead assembly 104 may be maintained at higher temperatures usingreadily available heat exchanging fluids.

FIG. 3 is a partial cross sectional view of another embodiment of ashowerhead assembly. The showerhead assembly 304 comprises a top plate330, mid-plate 310, an upper bottom plate 333A and a lower bottom plate333B which are coupled together. The mid-plate 310 and upper bottomplate 333A define the heat exchanging channel 375 through which the gasconduits 347 extend.

The mid-plate 310 includes a plurality of gas conduits 347 disposedtherethrough. The plurality of gas conduits 347 are disposed in themid-plate holes 340 and extend down through heat exchanging channel 375and into the bottom plate holes 350 located in upper bottom plate 333A.The gas conduits 347, which are aluminum tubes, are sealably coupled tothe mid-plate 310 and wall 380 in the upper bottom plate 333A by use ofa brazing or a welding technique to prevent the heat exchanging fluidfrom entering the first plenum 344 or the second plenum 345. The gasconduits 347 are sealably coupled to the mid-plate 310, wall 380 andwall 385 to assure that the fluids flowing through the first plenum 344,second plenum 345 and heat exchanging channel 375 are all isolated fromeach other. The first plenum 344 is fluidly coupled to the processingregion 308 through the conduits 381 formed in the wall 385 of the lowerbottom plate 333B. The upper bottom plate 333A and a lower plate 333Bare sealably coupled together to form the first plenum 344, and toprevent the material delivered from the source 331A from leaking fromregions of the showerhead assembly 304. Alternatively, the upper plate333A and lower plate 333B may be a single, unitary plate.

The top plate 330, the mid-plate 310, upper bottom plate 333A and lowerbottom plate 333B are formed from a metal, such as 316L stainless steel.It is contemplated that the top plate 330, the mid-plate 310, upperbottom plate 333A and lower bottom plate 333B may be formed from othermaterials as well, such as INCONEL®, HASTELLOY®, electroless nickelplated aluminum, pure nickel, and other metals and alloys resistant tochemical attack, or even quartz. Additionally, it is contemplated thatgas conduits 347 may be formed from a material other than aluminum, suchas stainless steel.

The top plate 330 contains a blocker plate 361 that is adapted to evenlydistribute the flow of the process gas 355 before the process gas 355enters the second plenum 345. In this configuration, the process gas 355is delivered to second plenum 345 from the source 332A via gas line 332and holes 362 formed in the blocker plate 361. The process gas 355 thenflows into a plurality of mid-plate holes 340 disposed in mid-plate 310and into gas conduits 347, which are in fluid communication with theprocessing region 308.

Each of the gas conduits 381 are concentric with the outlet of the gasconduits 347. In one example, the gas conduits 347 and gas conduits 381are both cylindrical in shape. A first end of each gas conduit 347 isdisposed in a mid-plate hole 340 and the first end of gas conduit 347 issuitably coupled (e.g., brazed, welded and/or press fit) to mid-plate310 so that a fluid seal is formed between the gas conduit 347 andmid-plate 310. Further, a second portion of each gas conduit 347 isdisposed within plate hole 350 of the upper bottom plate 333A such thatthe gas conduit 347 is sealably connected (e.g., brazed, welded and/orpress fit) to the wall 380 of the upper bottom plate 333A. The firstplenum 344 contains first process gas 354 which flows out of a pluralityof conduits 381 and into the processing region 108.

FIGS. 4A, 4B and 4C are schematic bottom views of the showerheadassemblies shown in FIGS. 2 and FIG. 3 according to embodiments of thepresent invention. FIG. 4A is a partial schematic bottom view of theshowerhead assembly shown in FIG. 3. In this configuration of showerheadassembly 304, an array of concentric gas conduits (i.e., gas conduit 347and gas conduits 381) are formed in the showerhead face 383 to evenlydistribute and mix the process gas prior to delivery to the surface of asubstrate.

FIG. 4B is a partial schematic bottom view of the showerhead assemblyshown in FIG. 2 according to one embodiment of the invention. In thisconfiguration of showerhead assembly 104, an array of gas conduits 247and gas conduits 281 are formed in the showerhead face 283 to evenlydistribute and mix the process prior to delivery to the surface of asubstrate. In this configuration, the gas conduits 247 and gas conduits281 are adjacently configured in a hexagonal close pack orientation.

FIG. 4C is a partial schematic bottom view of the showerhead assemblyshown in FIG. 2 according to another embodiment of the invention. Inthis configuration a radial array of gas conduits 247 and gas conduits281 are formed in the showerhead face 283 to evenly distribute and mixthe process gas prior to delivery to the surface of a substrate. In thisconfiguration, the radial array comprises an interleaved circular arrayof gas conduits 247 and gas conduits 281 that are concentric about thecenter of the showerhead assembly. The embodiments shown in FIGS. 4A, 4Band 4C are not meant to be limiting in scope, but rather, illustratesome of the possible combinations of gas conduits 247, 281, 347 and 381.

The showerhead assembly described herein may be advantageously used insubstrate processing, especially metal organic chemical vapordepositions or hydride vapor phase epitaxy processes. With reference toFIG. 3, a metal organic vapor deposition process will be described. Inthe metal organic chemical vapor deposition process, a process gas 354at a first temperature is introduced to a first plenum 344 of theshowerhead apparatus 304. The process gas 354 is then flown into aprocessing region 308. A process gas 355 at a second temperature isintroduced to a second plenum 345 of the showerhead apparatus 304. Theprocess gas 355 is then flown into the processing region 308 through gasconduits 347. A heat exchanging fluid is introduced to a heat exchangingchannel 375 disposed between the first plenum 344 and the second plenum345. The process gas 354 and the process gas 355 are reacted in theprocessing region 108 to form a film on a substrate. It is to beunderstood that process gas 354 and process gas 355 may be flownsequentially or simultaneously. Additionally, it is to be understoodthat the heat exchanging fluid may be introduced to the heat exchangingchannel prior to, during, or after flowing the process gases 354, 355 tothe processing region.

The process gas 354 which is delivered to first plenum 344 may comprisea Group V precursor, and process gas 355 which is delivered to secondplenum 345 may comprise a Group III precursor. Alternatively, theprecursor delivery may be switched so that the Group V precursor isrouted to second plenum 345 and the Group III precursor is routed tofirst plenum 344. The choice of first or second plenum 344, 345 for agiven precursor may be determined in part by the distance of the plenumfrom the heat exchanging channel 375 and the desired temperature rangeswhich may be maintained for each plenum and the precursor therein. Thus,examples of processes gases provided to the first plenum 344 or secondplenum 345 are not meant to be limiting in scope, rather, the examplesare provided merely for explanatory purposes. It is to be understoodthat embodiments described herein are not to be restricted to certainprocesses gases provided to either the first plenum 344 or second plenum345 without specific recitation.

Gas source 332A is configured to deliver a process gas 355 to the firstplenum 345. Process gas 355 is a metal organic precursor, such asgallium chloride. Other metal organic precursors, including Group IIIprecursors such as trimethylgallium (TMG), trimethyl aluminum (TMAI) andtrimethyl indium (TMI), are contemplated. Group III precursors havingthe general formula MX₃ may also be used, where M is a Group III element(e.g., gallium, aluminum, or indium) and X is a Group VII element (e.g.,bromine, chlorine or iodine). Source 331A is configured to deliver aprocess gas 354, such as ammonia, to the second plenum 344. It iscontemplated that other process gasses, such as nitrogen (N₂) orhydrogen (H₂) may be used.

Process gas 354 and process gas 355 are reacted to deposit a material,such as gallium nitride, on a substrate. It is contemplated that othermaterials may also be deposited on a substrate, such as aluminumnitride, indium nitride, aluminum gallium nitride and indium galliumnitride. Additionally, dopants, such as silicon (Si) or magnesium (Mg),may be added to the films. The films may be doped by adding smallamounts of dopant gases during the deposition process. For silicondoping, silane (SiH₄) or disilane (Si₂H₆) gases may be used, forexample, and a dopant gas may include Bis(cyclopentadienyl) magnesium(Cp₂Mg or (C₅H₅)₂Mg) for magnesium doping.

The deposition of material on a substrate generally occurs attemperatures greater than about 20 degrees Celsius. Thus, it may bedesirable to heat the process gases prior to deposition so that lamps orresistive heaters are not the sole means of providing heat. This allowsfor more control over deposition temperatures, resulting in a moreuniform deposition. However, some process gases cannot always be heatedto a desired temperature prior to material deposition because theprecursor contained within the process gas could decompose. If theprecursor undesirably decomposes, deposition of material could occur inlocations other than a substrate surface, for example, on interiorsurfaces of the showerhead assembly 304. Deposition within theshowerhead assembly 304 can affect gas flow, or could flake off, whichcould therefore affect deposition uniformity of a material on asubstrate. Thus, deposition of a material on interior surfaces of theshowerhead assembly 304 is undesirable.

One advantage of positioning heat exchanging channel 375 between thefirst plenum 344 and the second plenum 345 is the ability to delivermultiple precursors to the processing region 308 at differenttemperatures. Since the heat exchanging channel 375 is positionedbetween the first plenum 344 and the second plenum 345, only oneprecursor travels across the heat exchanging channel 375. Thus,precursor temperatures can be desirably affected by heat exchangingfluid provided to the heat exchanging channel 375 through inlet conduit371. For example, source 331A may contain a Group V precursor and may beheated in supply line 331 while being delivered to the showerheadassembly 304. The process gas then enters the first plenum 344 and theprocessing region 308 without crossing the heat exchanging channel 375.Thus, the temperature of the Group V precursor remains substantially atthe elevated temperature caused by the heated supply lines. Additionallyor alternatively, the temperature of the process gas in the first plenum344 could be increased by heat radiated from the processing region 308,thus pre-heating the process gas before delivery to the process region.Heating of the process gas allows a reaction to occur at an elevatedtemperature without requiring lamps disposed below the chamber to be thesole method of heating the interior of the chamber.

In one example, a Group III precursor, such as trimethylgallium isdelivered to the second plenum 345 at a first temperature. Sincetrimethylgallium can decompose at elevated temperatures, thus depositinggallium on interior surfaces of the showerhead assembly 304, it ispreferable that the first temperature is sufficiently low to preventgallium deposition. The trimethylgallium is then introduced to theprocessing region 308 through gas conduits 347. Since gas conduits 347are positioned in contact with a heat exchanging fluid present in theheat exchanging channel 375, the temperature of the trimethylgalliumpresent in the gas conduits 347 is prevented from increasing to atemperature where decomposition and deposition could occur. A Group Vprecursor, such as ammonia, is delivered to the processing region 308through the first plenum 344 at a second temperature which is greaterthan the first temperature. Since the Group V precursor does not passthrough the heat exchanging channel 375, the Group V precursor entersthe processing region 308 without a substantial loss of heat. Thus, theGroup V precursor enters the processing region 308 at the secondtemperature, while the Group II precursor enters the processing regionat the first temperature (as maintained by the heat exchanging fluid).Thus, by positioning a heat exchanging channel 375 between a firstplenum 344 and a second plenum 345, temperature-sensitive precursors canbe delivered to the process region 308 without decomposing in undesiredlocations. Furthermore, precursors which are not temperature sensitivecan be delivered at increased temperatures to allow more control overdeposition processes by providing an additional means of controllingprocess gas temperatures.

Additionally, since process gas temperatures can be affected by heatedgas lines, heat exchanging fluid, and lamps disposed beneath thechamber, the temperature of the process gases and of the substrateduring processing can be more accurately controlled and fine-tuned. Thecombination of multiple heating sources allows for greater processcontrol and thus deposition uniformity. Also, by disposing heatexchanging channel 375 within the showerhead assembly 304, thetemperature of the showerhead assembly 304 can be maintained by removingany excess heat transferred to the showerhead assembly 304 from theheated Group V precursor. Thus, heat-induced damage, such as warping orwear of the showerhead, can be prevented. Additionally, since a heatedprocess gas does not travel through the heat exchanging channel 375,thermal efficiency is increased. If a heated gas was to pass through theheat exchanging channel 375, heat would be removed. Thus, lamps wouldhave to reheat the process gas by providing heat to the interior of thechamber which was previously removed by the heat exchanging fluid,thereby reducing thermal budget and increasing process cost.

The showerhead assembly embodiments described herein for metal organicchemical vapor deposition applications may be adapted for use in ahydride vapor phase epitaxy or metal-organic chemical vapor deposition,among other processes. The hydride vapor phase epitaxy process offersseveral advantages in the growth of some Group III-IV films, galliumnitride in particular, such as high growth rate, relative simplicity,and cost effectiveness. In this technique, the growth of gallium nitrideproceeds due to the high temperature, vapor phase reaction betweengallium chloride and ammonia. The ammonia may be supplied from astandard gas source, while the gallium chloride is produced by passing ahydride-containing gas, such as HCl, over a heated liquid galliumsupply. The two gases, ammonia and gallium chloride, are directedtowards a heated substrate where they react to form an epitaxial galliumnitride film on the surface of the substrate. In general, the hydridevapor phase epitaxy process may be used to grow other Group III-nitridefilms by flowing a hydride-containing gas (such as HCl, HBr, or HI) overa Group III liquid source to form a Group III-halide gas. Then, theGroup III-halide gas is mixed with a nitrogen-containing gas, such asammonia, to form a Group III-nitride film.

Still with reference to FIG. 3, when showerhead assembly 304 is adaptedfor hydride vapor phase epitaxy, a heated source boat (not shown) may becoupled to the first plenum 344 or the second plenum 345. The heatedsource boat may contain a metal (e.g., gallium) source which is heatedto the liquid phase, and a hydride-containing gas (e.g., hydrochloricacid) may flow over the metal source to form a Group III-halide gas,such as gallium chloride. The Group III-halide gas and anitrogen-containing gas, such as ammonia, may then be delivered to firstand second plenums 344, 345 of showerhead assembly 304 via supply lines331, 332 for injection into the processing region 308 to deposit a GroupIII-nitride film, such as gallium nitride, on a substrate. Additionallyor alternatively, one or more supply lines 331, 332 may be heated todeliver the precursors from an external heated boat to chamber 302.Also, an inert gas, which may be hydrogen, nitrogen, helium, argon orcombinations thereof, may be flowed between first and second hydridevapor phase epitaxy process gases to help keep the precursors separatedbefore reaching a substrate. The HVPE process gases may also includedopant gases.

Nom Advantages of the present invention include, but are not limited to,an improved deposition apparatus and processes which provide greaterprocess control and uniformity. A heat exchanging channel disposedwithin a showerhead assembly allows for temperature control of theshowerhead assembly, and may increase the usable life of the showerheadassembly by reducing heat-induced damage thereto. Additionally, since atleast one process gas is not required to travel across or through theheat exchanging channel, one process gas can be delivered to aprocessing region at a temperature greater than another processing gas.This allows for process gases to be supplied to a process region at amore accurate temperature. Additionally, since the process gas does notundesirably have heat removed, the overall thermal budget of the processis decreased because lamps below the chamber are not required to supplyenergy to the process gas or chamber which was previously removed by aheat exchanging fluid. Thus, since at least one process gas does nottravel through the heat exchanging channel, processes within the processchamber are thermally more efficient.

Furthermore, since the invention provides at least two ways ofcontrolling process temperature (accurate heating of process gas priorto delivery to the showerhead apparatus, and heat supplied from lampsdisposed below the chamber), processes within the chamber can be moreaccurately controlled. The greater level of control due to the multipleheat sources causes greater process uniformity across individualsubstrates, and greater uniformity from substrate to substrate duringprocessing. Thus, since substrate uniformity is increased, a greaternumber of substrates and/or larger substrates can be processed comparedto traditional metal organic chemical vapor deposition chambers. Theincreased processing ability increases throughput and reduces processingcost per substrate.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An apparatus, comprising: a lower bottom plate; an upper bottom platepositioned above the lower bottom plate, the upper bottom plate and thelower bottom plate defining a first plenum; a mid-plate positioned abovethe upper bottom plate, the mid-plate and the upper bottom platedefining a heat exchanging channel for containing a heat exchangingfluid; a top plate positioned above the mid-plate, the top plate and themid-plate defining a second plenum; and a plurality of first gasconduits extending from the second plenum through the heat exchangingchannel and the first plenum, each of the plurality of first gasconduits in fluid communication with the second plenum and a processingregion of a processing chamber.
 2. The apparatus of claim 1, wherein thetop plate, the mid-plate, the upper bottom plate, the lower bottom plateand the plurality of first gas conduits comprise stainless steel.
 3. Theapparatus of claim 2, wherein the mid-plate and the upper bottom plateboth have holes disposed therethrough, and wherein the plurality offirst gas conduits are positioned within the holes of the mid-plate andthe upper bottom plate.
 4. The apparatus of claim 3, further comprisinga plurality of second gas conduits, wherein the first gas conduits andthe second gas conduits are positioned in a hexagonal close packorientation on a surface of the lower bottom plate.
 5. The apparatus ofclaim 3, further comprising a plurality of second gas conduits, whereinthe first gas conduits and the second gas conduits form concentriccircular arrays on a surface of the lower bottom plate.
 6. An apparatus,comprising: a lower bottom plate; an upper bottom plate positioned abovethe lower bottom plate, the upper bottom plate and the lower bottomplate defining a first plenum; a plurality of first gas conduits influid communication with the first plenum and a processing region of aprocess chamber; a mid-plate positioned above the upper bottom plate,the mid-plate and the upper bottom plate defining a heat exchangingchannel for containing a heat exchanging fluid; a top plate positionedabove the mid-plate, the top plate and the mid-plate defining a secondplenum; and a plurality of second gas conduits in fluid communicationwith the second plenum and the processing region, the plurality ofsecond gas conduits extending through the first plenum and the heatexchanging channel, and each of the first gas conduits having a secondgas conduit that is disposed within the boundary of the first gasconduit.
 7. The apparatus of claim 6, wherein each of the first gasconduits has a second gas conduit that is concentrically arrangedtherewith.
 8. The apparatus of claim 6, wherein the plurality of firstand second gas conduits have a cylindrical configuration.
 9. Theapparatus of claim 6, wherein the top plate includes a blocker platepositioned above the second plenum.
 10. The apparatus of claim 9,wherein the mid-plate and the upper bottom plate both have holesdisposed therethrough, and wherein the plurality of second gas conduitsare positioned within the holes of the mid-plate and the upper bottomplate.
 11. The apparatus of claim 10, wherein the top plate, themid-plate, the upper bottom plate and the lower bottom plate comprisestainless steel, aluminum or nickel.
 12. The apparatus of claim 11,wherein the second gas conduits comprise aluminum.
 13. A method,comprising: flowing a first gas through a first plenum of a showerheadapparatus and into a processing region of a chamber; flowing a secondgas through a second plenum of the showerhead apparatus and into theprocessing region of the chamber, the second plenum fluidly coupled tothe processing region through a plurality of gas conduits; introducing aheat exchanging fluid to a heat exchanging channel disposed between thefirst plenum and the second plenum, wherein the plurality of gasconduits extend through the heat exchanging channel; and reacting thefirst gas and the second gas in the processing region to form a film onthe substrate, wherein the temperature of the first gas is greater thanthe temperature of the second gas when the first gas and the second gasenter the processing region.
 14. The method of claim 13, wherein thefirst gas comprises a Group III element and the second gas comprises aGroup V element.
 15. The method of claim 14, wherein the first gascomprises gallium and the second gas comprises ammonia.